Low Magnesium Levels Reef Tank

[Chrisz]

Good morning all!

I have unfortunately let my tank go and am trying to get things under control again. I have a 97 gallon corner aquarium and have been using Reef Crystals, doing a 20 gallon water change weekly. My water parameters are as follows:

Date	11/21/2020​
PH	8.1
DKH	8
Calcium	412
Magnesium	880
Salinity	1.025
Phosphate	0.24
Nitrate	0
Nitrite	0
Ammonia	0
Temperature	79.8

I have been trying to get the magnesium levels up, i have been putting in 25 ml of Fluval Sea mag every other day measuring on the off day I am guessing I have about 100 gallons of water including the sump. The container says it should provide 5mg/L per dose, I cant seem to get the mag levels to budge, starting to wonder if my Red Sea test kit is not working. Thoughts, maybe I just need to dose more.

 

[Doctorgori]

just one suggestion (you might get multiple good answers)
perhaps try Brightwells Kalk+2 ...I use it along with Tropic Marins Part-C ....may even be overkill ...been working tho

 

[biophilia]

I can't speak to that specific magnesium product, but magnesium usually needs to be dosed in much higher volumes than you'd expect compared to products like 2 part solutions. 25ml feels pretty low to me for 100 gallons. For comparison, 12ml of Kent magnesium raises the Mg level of 10 gallons of water roughly 100ppm. If the Fluval mag is a similar concentration, you'd be looking at adding 120+ml just to get your Mg near 1000. I'd double check the dosing instructions (and also maybe reference a different test kit just to be sure).

 

[Chrisz]

It really seemed like a lot of mag I was using...I have some Kent Marine also, the directions say 1ml per gallon think I will give that one a try

 

[Chrisz]

Just an update...found out my mag is just fine, my test kits where bad. 2 year old test kit, got a new one now

 

[blasterman]

Yeah.. was going there.

Mag tests kits can be gimpy and while RC is variable in terms of alk its mag tends to test pretty consistent with it. Typically ~1250 -1300

To get mag out of alignment with calcium requires a significant amount of calcium dosing without mag dosing or even heavier kalk dosing.

 

[Randy Holmes-Farley]

just one suggestion (you might get multiple good answers)
perhaps try Brightwells Kalk+2 ...I use it along with Tropic Marins Part-C ....may even be overkill ...been working tho

I doubt he has magnesium that low, but Brightwell kalk+2 will NEVER solve the problem. Terrible product claims. less magnesium than ordinary calcium hydroxide, almost none anyway by their own analysis, and it cannot dissolve into limewater even if there was more. Designed by a Marine Biologist. He missed chemistry class, apparently.

 

[Doctorgori]

I doubt he has magnesium that low, but Brightwell kalk+2 will NEVER solve the problem. Terrible product claims. less magnesium than ordinary calcium hydroxide, almost none anyway by their own analysis, and it cannot dissolve into limewater even if there was more. Designed by a Martine Biologist. He missed chemistry class, apparently.

there goes your paid endorsement with Brightwell I was gonna arrange for you
Still I haven’t had to supplement Mg in months with that Kalk 2 but admittedly it cudda been the Part-c for all I know

 

[Randy Holmes-Farley]

there goes your paid endorsement with Brightwell I was gonna arrange for you
Still I haven’t had to supplement Mg in months with that Kalk 2 but admittedly it cudda been the Part-c for all I know

Magnesium sulfate is the main ingredient in part C.